164 Single-Geared Drilling Machine. screw to a projecting arm^ and provided with slots for bolts, as in the lathe face plate. The pillar g, which supports f, has rack teeth turned upon it, so that the lifting apparatus may always remain in gear, whatever the position of arm y; The lifting gear is as follows: A spindle q turns a worm, gearing into wheel/, which has on its axis a pinion engaging with teeth on the pillar g. The handle k serves either for spindle q, or for hand drilling when applied to the mandrel. Some machines have a plain pillar, as in the next example. A very deep piece of work is accommodated by bolting to the foot or bed, and swinging the table out of the way. In double-geared drills the countershaft is usually self-con- tained, as at m ; and the pulley n is driven from main shaft; the fast and loose pullies lying side by side, and the fork being moved by handle /. The Single-Geared Drilling Machine in Fig. 167 needs little further description. Back gear is dispensed with, and the cone pulley A keyed to the mandrel. Hand drilling is pro- vided for by the handle B on fly-wheel c. s is the hollow sleeve driven by mitre wheels; and a feed screw at D takes the place of the rack, being provided with a long key-way, while a key E (shewn 1 black) is fixed to spur wheel F, so that a feed may be obtained at any height of drill spindle. The feed screw further passes through a nut G, fixed to the casting H, and a rotation of F will therefore raise or lower the screw; such Dotation being effected by turning the hand-wheel on spindle j, ther latter carrying a pinion K gearing into F. A socket L in drill spindle receives a cylindrical projection on the screw, in which a race is turned; and a pin M, passing through the spindle tangential to the race, allows the screw to lift the spindle without affecting the rotation of the latter. In the best machines the feed screw is a hollow sleeve. The table and supporting arm are similar to the last example, the lifting gear consisting of a handle N and worm p, worm-wheel Q, and rack pinion, the rotation of the last lifting or lowering the arm. The rack R is a sort of strut fitted between the top and bottom collars of the pillar, but otherwise loose. If the table be moved horizontally the rack is carried round the pillar, and remains in gear with the pinion in all positions.